Musculus deltoideus

Musculus Deltoideus is a large, triangular muscle occupying the upper arm and the shoulder giving it a rounded shape. The muscle is named after the Greek letter delta, which is shaped like an equilateral triangle. It is commonly referred to as the deltoid muscle.

Anatomy

The deltoid muscle originates from three distinct areas of the body: the anterior border and upper surface of the lateral third of the clavicle, the lateral edge of the acromion, and the lower edge of the spine of the scapula. It inserts at the deltoid tuberosity on the middle of the lateral aspect of the humerus.

Function

The deltoid muscle functions to help in the movement of the upper limbs. It is the primary muscle responsible for arm rotation and allows for a variety of arm movements. The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. The anterior deltoid is involved in shoulder flexion. The posterior fibers are involved in shoulder abduction when the shoulder is internally rotated, and are also involved in shoulder extension and external rotation.

Clinical Significance

Injury to the deltoid muscle or its nerve supply can cause significant impairment of the arm and shoulder function. This can result from direct trauma, overuse, or neurological conditions. Treatment typically involves physical therapy, medication, and in some cases, surgery.

See Also

• Muscular system
• Human anatomy
• Shoulder